JP2008199341A - Electrostatic transducer, ultrasonic speaker, speaker device, audio signal reproducing method by electrostatic transducer, directional sound system, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic transducer capable of increasing electrostatic force while securing an amplitude distance for a diaphragm without unnecessarily raising voltages to be applied to a fixed electrode and the diaphragm. <P>SOLUTION: The electrostatic transducer includes the diaphragm which has a vibrating electrode layer, and an electrode which has an electrode portion to generate electrostatic force with a voltage applied between a through hole and the diaphragm adjacently to the through hole. The electrode is disposed opposite to the diaphragm, and at least a part of the electrode portion has such a shape that the distance between a surface of a vibrating portion of the diaphragm in a non-vibrating state and a surface of the electrode portion is larger at the center portion of the vibrating part of the diaphragm than at an end portion. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrostatic transducer capable of increasing the electrostatic force while ensuring the amplitude distance of the vibrating membrane between the vibrating membrane and the electrode, without increasing the voltage applied to the fixed electrode and the vibrating membrane more than necessary. The present invention relates to an ultrasonic speaker, a speaker device, an audio signal reproduction method using an electrostatic transducer, a directional acoustic system, and a display device.

  An electrostatic transducer used for an ultrasonic speaker or the like includes an electrostatic transducer called a pull type shown in FIG. 20 (see, for example, Patent Document 1), and an electrostatic type called a push pull type shown in FIG. There is a transducer (see, for example, Patent Document 2).

  The pull-type electrostatic transducer shown in the cross-sectional view of FIG. 20A includes a vibrating film 22, a fixed electrode 51 formed of a conductor having a convex portion 51C that is in close contact with the vibrating film 22, and a DC bias power source. 28 and a signal source for generating an alternating current signal 29. As shown in FIG. 20B, the vibrating film 22 is formed by sandwiching a vibrating electrode layer 22A, which is a conductive layer, between dielectric films (insulating layers) 22B.

  A constant DC bias voltage is always applied between the vibrating electrode layer 22A and the fixed electrode 51 by a DC bias power supply 28 capable of adjusting the voltage, and the convex portion of the fixed electrode 51 is generated by the electrostatic force generated by this electric field. The vibration electrode layer 22A is adsorbed to 51C, and is in close contact except for the cavity portion (electrostatic force generation portion) 52 formed between the vibration electrode layer 22A and the fixed electrode 51. In addition, the fixed electrode 51 is formed with a vent portion 54 that communicates from the cavity 52 to the outside.

  In the above configuration, when a DC bias voltage is applied between the vibrating electrode layer 22 </ b> A of the vibrating film 22 and the fixed electrode 51 by the DC bias power supply 28, the vibrating electrode layer 22 </ b> A of the vibrating film 22 is protruded from the fixed electrode 51. Adsorbed to 51C. In this state, an AC signal 29 is applied between the vibrating electrode layer 22A and the fixed electrode 51, whereby the vibrating electrode layer 22A and the electrode portion (surface facing the vibrating portion of the vibrating membrane) 53 of the fixed electrode 51, The electrostatic force acts between the two and the vibrating membrane 22 is driven by the AC signal 29 and vibrates.

  FIG. 20C shows the vibration state of the vibrating membrane 22 when the negative (−) side output of the AC signal 29 is applied to the vibrating electrode layer 22A, and FIG. 20D shows the AC signal. 29 shows a vibration state of the vibration film 22 when the positive (+) side output of 29 is applied.

  In the case of the state shown in FIG. 20C, the potential difference between the fixed electrode 51 and the vibrating electrode layer 22A increases, and a strong electrostatic force (attraction force) acts between the fixed electrode 51 and the vibrating electrode layer 22A. The central portion of the vibrating electrode layer 22 </ b> A is drawn toward the fixed electrode 51. In the case of the state shown in FIG. 20D, the potential difference between the fixed electrode 51 and the vibrating electrode layer 22A is reduced, and the electrostatic force (attraction force) between the fixed electrode 51 and the vibrating electrode layer 22A is weakened. The central portion of the vibrating electrode layer 22A is pulled back in the direction opposite to the fixed electrode 51 by an elastic restoring force. In this way, the vibrating electrode layer 22A vibrates according to the AC signal 29 and outputs sound waves.

  As described above, the electrostatic transducer shown in FIG. 20 is called a pull-type electrostatic transducer because the vibrating membrane receives an electrostatic attractive force from one direction. The advantages of this pull type electrostatic transducer are that the opening area is large and that it is easy to obtain sound pressure, and the disadvantage is that the distortion of the output waveform is large. (Because it vibrates with electrostatic attractive force and elastic restoring force).

  A push-pull electrostatic transducer shown in FIG. 21A includes a vibrating membrane 22 having a vibrating electrode layer 22A, a front-side fixed electrode 51A provided to face each surface of the vibrating membrane 22, and It has a pair of fixed electrode which consists of back side fixed electrode 51B. As shown in FIG. 21B, the vibration film 22 is formed so that a vibration electrode layer 22A, which is a conductive layer, is sandwiched between dielectric films 22B.

  The front side fixed electrode 51A sandwiching the vibrating membrane 22 is provided with a plurality of vent holes (through holes) 54A, and the back side fixed electrode 51B is provided with a vent hole provided in the front side fixed electrode 51A. A vent hole portion (through hole) 54B having the same shape is provided at a position facing 54A. The front-side fixed electrode 51A and the back-side fixed electrode 51B are in close contact with each other except for the cavity portions (electrostatic force generating portions) 52A and 52B formed between the vibrating electrode layer 22A and the fixed electrodes 51A and 51B. The vibrating membrane 22 and the fixed electrodes 51A and 51B are configured so as to face each other through the hollow portions 52A and 52B.

  The DC bias power supply 28 is a power supply for applying a DC bias voltage to the vibrating electrode layer 22A, and the AC signals 29A and 29B are applied between the front fixed electrode 51A and the rear fixed electrode 51B. Signal. With the above configuration, the AC signals 29A and 29B having the same amplitude and inverted phases with respect to the center tap are applied to the front side fixed electrode 51A and the back side fixed electrode 51B. As a result, an electrostatic force acts between the vibrating electrode layer 22A and the electrode portions (surfaces facing the vibrating portion of the vibrating membrane) 53A, 53B of the fixed electrodes 51A, 51B, and the vibrating membrane 22 receives the AC signals 29A, 29B. Driven and vibrated.

  FIG. 21A shows the amplitude state of the vibrating membrane 22 when the AC signal is zero (0), and the vibrating membrane 22 is neutral (middle of the front-side fixed electrode 51A and the rear-side fixed electrode 51B). In position.

  FIG. 21C is a diagram illustrating a vibration state of the vibrating membrane 22 when a positive voltage of an AC signal is applied to the front fixed electrode 51A and a negative voltage of the AC signal is applied to the rear fixed electrode 51B. Yes, the central portion of the vibrating electrode layer 22A of the vibrating membrane 22 has a back surface due to an electrostatic force (attraction force) between the back side fixed electrode 51B and an electrostatic force (repulsive force) between the front side fixed electrode 51A. It is attracted in the direction of the side fixed electrode 51B.

FIG. 21D is a diagram illustrating a vibration state of the vibrating membrane 22 when a negative voltage of an AC signal is applied to the front fixed electrode 51A and a positive voltage of the AC signal is applied to the rear fixed electrode 51B. Yes, the central portion of the vibrating electrode layer 22A of the vibrating membrane 22 is formed on the front side by an electrostatic force (attraction force) between the front side fixed electrode 51A and an electrostatic force (repulsive force) between the rear side fixed electrode 51B. It is drawn in the direction of the fixed electrode 51A.
In this way, the vibrating membrane 22 vibrates according to the AC signal and outputs sound waves, and the sound waves generated by the vibrating membrane 22 are released to the outside through the vent portions 54A and 54B provided in the fixed electrodes 51A and 51B. The

As described above, the electrostatic transducer shown in FIG. 21 is called a push-pull electrostatic transducer because the vibrating membrane receives an electrostatic force from both the upper and lower fixed electrodes and vibrates. The advantage of this push-pull type electrostatic transducer is that the distortion of the output waveform is small (because the electrostatic force acts symmetrically between positive and negative).
JP 2005-117103 A JP 2005-354472 A

  In the electrostatic transducer described above, it is necessary to increase the amplitude of the diaphragm, that is, to increase the electrostatic force in order to increase the sound pressure. In general, to increase the electrostatic force, there are a method of increasing the voltage applied to the fixed electrode and the diaphragm, and a method of reducing the distance between the vibration surface of the diaphragm and the fixed electrode corresponding to the vibration surface of the diaphragm. .

  The method of increasing the voltage causes a problem of increasing power consumption. Then, in the method of reducing the distance between the vibration surface of the vibration film and the fixed electrode corresponding to the vibration surface of the vibration film, if the distance is too small, as shown in FIG. The end portion 61 of the fixed electrode 51A) and the vibrating membrane 22 come into contact with each other, so that a sufficient amplitude distance cannot be secured. As described above, in the method of reducing the distance between the vibration surface of the vibration film and the fixed electrode corresponding to the vibration surface of the vibration film, the electrostatic force can be increased, but the vibration film and the fixed electrode have a hitting amplitude limit.

  The present invention has been made to solve such a problem, and an object of the present invention is to reduce the amplitude distance of the diaphragm without increasing the voltage applied to the fixed electrode or the diaphragm more than necessary in the electrostatic transducer. An electrostatic transducer, an ultrasonic speaker, a speaker device, an audio signal reproduction method using a capacitive transducer, a directional acoustic system, and a display device can be provided.

The present invention has been made to solve the above problems, and an electrostatic transducer according to the present invention includes a vibrating membrane having a vibrating electrode layer, a through hole and the vibrating membrane adjacent to the through hole. And an electrode having an electrode part that generates an electrostatic force by a voltage applied to the electrode, wherein the electrode is disposed to face the vibration film, and at least a part of the electrode part is a vibration part of the vibration film. The distance between the surface during non-vibration and the surface of the electrode portion is such that the distance at the center is larger than at the end of the vibrating portion of the vibrating membrane.
With such a configuration, in the electrostatic transducer, at least a part of the electrode portion of the fixed electrode portion (electrostatic force generation surface facing the vibration membrane) is disposed on the surface of the electrode portion and the vibration membrane (surface during non-vibration). The distance between the center portion and the center portion is larger than the end portion (the end portion of the vibrating portion of the vibrating membrane). Thereby, the electrostatic force can be increased while ensuring the amplitude distance of the diaphragm without increasing the voltage applied to the fixed electrode and the diaphragm more than necessary.

Further, in the electrostatic transducer according to the present invention, at least a part of the electrode part is formed on the vibration part of the vibration film at a distance between the surface of the vibration part of the vibration film when not vibrating and the surface of the electrode part. It is the shape of the inclined surface where distance becomes large as it goes to a center part from an edge part, It is characterized by the above-mentioned.
With such a configuration, an inclined surface is provided on at least a part of the electrode portion of the fixed electrode, and the distance between the electrode portion and the surface of the vibrating membrane (the surface during non-vibration) is the end portion (the vibration portion of the vibrating membrane). As the distance increases from the edge to the center, the electrostatic force can be increased while ensuring the amplitude distance of the diaphragm without increasing the voltage applied to the fixed electrode or diaphragm more than necessary. it can.

Further, in the electrostatic transducer according to the present invention, at least a part of the electrode part is formed on the vibration part of the vibration film at a distance between the surface of the vibration part of the vibration film when not vibrating and the surface of the electrode part. It is a shape of a curved surface whose distance increases from the end toward the center.
With such a configuration, a curved surface is provided on at least a part of the electrode portion of the fixed electrode, and the distance between the electrode portion and the surface of the vibrating membrane (the surface during non-vibration) is the end portion (the end of the vibrating portion of the vibrating membrane). In this case, the electrostatic force can be increased while ensuring the amplitude distance of the diaphragm without increasing the voltage applied to the fixed electrode and diaphragm more than necessary. .

Further, in the electrostatic transducer according to the present invention, at least a part of the electrode part is formed on the vibration part of the vibration film at a distance between the surface of the vibration part of the vibration film when not vibrating and the surface of the electrode part. It has a step-like shape in which the distance increases from the end toward the center.
With such a configuration, in the electrostatic transducer, at least a part of the electrode portion of the fixed electrode has a staircase shape, and the distance between the electrode portion and the surface of the vibrating membrane (the surface during non-vibration) is the end portion (vibration). (The end of the vibrating portion of the membrane) increases from the center to the central portion, so that the amplitude applied to the vibrating membrane can be secured while maintaining the amplitude distance of the vibrating membrane without increasing the voltage applied to the fixed electrode and the vibrating membrane more than necessary. Power can be increased.

Further, in the electrostatic transducer according to the present invention, at least a part of the electrode part is formed on the vibration part of the vibration film at a distance between the surface of the vibration part of the vibration film when not vibrating and the surface of the electrode part. It is a shape in which at least two or more of an inclined surface, a curved surface, and a staircase shape are combined, the distance being greater in the center portion than in the end portion.
With such a configuration, at least a part of the electrode portion of the fixed electrode has a shape obtained by combining at least two of an inclined surface, a curved surface, and a stepped shape, and the surface of the electrode portion and the vibrating membrane (non-vibration) Since the distance from the surface of the time increases from the end (the end of the vibrating portion of the vibrating membrane) toward the center, this increases the voltage applied to the fixed electrode and the vibrating membrane more than necessary. The electrostatic force can be increased while ensuring the amplitude distance of the diaphragm.

The electrostatic transducer according to the present invention includes an electrode portion that generates an electrostatic force by a voltage applied between a vibrating membrane having a vibrating electrode layer and a through hole and the vibrating membrane adjacent to the through hole. A first electrode having a through hole and a second electrode having an electrode portion that generates an electrostatic force by a voltage applied between the through hole and the vibration film adjacent to the through hole. The electrode and the second electrode are disposed to face both surfaces of the vibrating membrane, respectively, and at least a part of the electrode portion includes a surface of the vibrating portion of the vibrating membrane during non-vibration and the electrode portion. In the distance from the surface, the distance increases from the end of the vibrating portion of the vibrating membrane toward the center.
With such a configuration, in the push-pull type electrostatic transducer configured by sandwiching the vibration membrane between the pair of electrodes, at least a part of the electrode portion of the fixed electrode portion is formed on the surface of the electrode portion and the vibration membrane ( The distance from the surface at the time of non-vibration increases from the end (the end of the vibrating portion of the vibrating membrane) toward the center. As a result, the electrostatic force can be increased while ensuring the amplitude distance of the diaphragm.

Further, in the electrostatic transducer according to the present invention, at least a part of the electrode portion is a portion of the vibrating portion of the front vibrating membrane at a distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. It is the shape of the inclined surface where distance becomes large as it goes to a center part from an edge part, It is characterized by the above-mentioned.
With such a configuration, in the push-pull type electrostatic transducer configured by sandwiching the vibrating membrane between the pair of electrodes, an inclined surface is provided on at least a part of the electrode portion of the fixed electrode, and the electrode portion and the vibrating membrane are provided. Since the distance from the surface (surface during non-vibration) increases from the end (end of the vibrating portion of the vibrating membrane) toward the center, the voltage applied to the fixed electrode and vibrating membrane The electrostatic force can be increased while securing the amplitude distance of the diaphragm without increasing the value more than necessary.

Further, in the electrostatic transducer according to the present invention, at least a part of the electrode part is formed on the vibration part of the vibration film at a distance between the surface of the vibration part of the vibration film when not vibrating and the surface of the electrode part. It is a shape of a curved surface whose distance increases from the end toward the center.
With such a configuration, in a push-pull type electrostatic transducer configured by sandwiching the vibrating membrane between a pair of electrodes, a curved surface is provided on at least a part of the electrode portion of the fixed electrode, and the electrode portion and the vibrating membrane are provided. Since the distance from the surface (the surface during non-vibration) increases from the end (the end of the vibrating part of the vibrating membrane) toward the center, the voltage applied to the fixed electrode and the vibrating membrane is thereby increased. The electrostatic force can be increased while ensuring the amplitude distance of the diaphragm without increasing it more than necessary.

Further, in the electrostatic transducer according to the present invention, at least a part of the electrode part is formed on the vibration part of the vibration film at a distance between the surface of the vibration part of the vibration film when not vibrating and the surface of the electrode part. It has a step-like shape in which the distance increases from the end toward the center.
With such a configuration, in the push-pull type electrostatic transducer configured by sandwiching the vibrating membrane between the pair of electrodes, at least a part of the electrode portion of the fixed electrode has a stepped shape, and the electrode portion and the vibrating membrane are Since the distance from the surface (the surface during non-vibration) increases from the end (the end of the vibrating part of the vibrating membrane) toward the center, the voltage applied to the fixed electrode and the vibrating membrane is thereby increased. The electrostatic force can be increased while ensuring the amplitude distance of the diaphragm without increasing it more than necessary.

Further, in the electrostatic transducer according to the present invention, at least a part of the electrode part is formed on the vibration part of the vibration film at a distance between the surface of the vibration part of the vibration film when not vibrating and the surface of the electrode part. The shape is a combination of at least two of an inclined surface, a curved surface, and a stepped shape whose distance increases from the end toward the center.
With such a configuration, in the push-pull type electrostatic transducer configured by sandwiching the vibrating membrane between the pair of electrodes, at least a part of the electrode portion of the fixed electrode has an inclined surface, a curved surface, or a stepped shape. The shape is a combination of at least two of them, and the distance between the electrode portion and the surface of the vibrating membrane (the surface during non-vibration) increases from the end portion (end portion of the vibrating portion of the vibrating membrane) toward the center portion. Thus, the electrostatic force can be increased while ensuring the amplitude distance of the diaphragm without increasing the voltage applied to the fixed electrode and the diaphragm more than necessary.

The electrostatic transducer according to the present invention includes an electrode portion that generates an electrostatic force by a voltage applied between a vibrating membrane having a vibrating electrode layer and a through hole and the vibrating membrane adjacent to the through hole. The electrode is disposed so as to face only one side of the vibrating membrane, and at least a part of the electrode portion includes a surface of the vibrating portion of the vibrating membrane when not vibrating and the electrode portion. In the distance from the surface, the distance increases from the end of the vibrating portion of the vibrating membrane toward the center.
..With such a configuration, in the pull-type electrostatic transducer in which the electrode is disposed so as to face only one side of the vibrating membrane, at least a part of the electrode portion of the electrode includes the electrode portion and the surface of the vibrating membrane ( The distance is increased from the end (the end of the vibrating portion of the vibrating membrane) toward the center of the non-vibrated surface. That is, since the distance between the surface of the vibrating membrane and the electrode portion of the fixed electrode is increased from the end of the vibrating portion of the vibrating membrane toward the central portion, the voltage applied to the fixed electrode and the vibrating membrane is thereby increased. The electrostatic force can be increased while ensuring the amplitude distance of the diaphragm without increasing it more than necessary.

Further, in the electrostatic transducer according to the present invention, at least a part of the electrode part is formed on the vibration part of the vibration film at a distance between the surface of the vibration part of the vibration film when not vibrating and the surface of the electrode part. It is the shape of the inclined surface where distance becomes large as it goes to a center part from an edge part, It is characterized by the above-mentioned.
With such a configuration, in the pull-type electrostatic transducer in which the electrode is disposed to face only one side of the vibrating membrane, an inclined surface is provided on at least a part of the electrode portion of the fixed electrode, and the electrode portion and the vibrating membrane are provided. Since the distance from the surface (surface at the time of non-vibration) increases from the end (end of the vibrating portion of the vibrating membrane) toward the center, the distance between the fixed electrode and the vibrating membrane The electrostatic force can be increased while securing the amplitude distance of the diaphragm without increasing the applied voltage more than necessary.

Further, in the electrostatic transducer according to the present invention, at least a part of the electrode part is formed on the vibration part of the vibration film at a distance between the surface of the vibration part of the vibration film when not vibrating and the surface of the electrode part. It is a shape of a curved surface whose distance increases from the end toward the center.
With such a configuration, in the pull-type electrostatic transducer in which the electrode is disposed so as to face only one side of the vibrating membrane, a curved surface is provided on at least a part of the electrode portion of the fixed electrode, and the electrode portion and the vibrating membrane Since the distance from the surface (the surface during non-vibration) increases from the end (the end of the vibrating portion of the vibrating membrane) toward the center, this adds to the fixed electrode and the vibrating membrane. Without increasing the voltage more than necessary, the electrostatic force can be increased while securing the amplitude distance of the diaphragm.

Further, in the electrostatic transducer according to the present invention, at least a part of the electrode part is formed on the vibration part of the vibration film at a distance between the surface of the vibration part of the vibration film when not vibrating and the surface of the electrode part. It has a step-like shape in which the distance increases from the end toward the center.
With such a configuration, in the pull-type electrostatic transducer in which the electrode is disposed so as to face only one side of the diaphragm, at least a part of the electrode part of the fixed electrode has a step shape, and the electrode part and the diaphragm are Since the distance from the surface (the surface during non-vibration) increases from the end (the end of the vibrating part of the vibrating membrane) toward the center, the voltage applied to the fixed electrode and the vibrating membrane is thereby increased. The electrostatic force can be increased while ensuring the amplitude distance of the diaphragm without increasing it more than necessary.

Further, in the electrostatic transducer according to the present invention, at least a part of the electrode part is formed on the vibration part of the vibration film at a distance between the surface of the vibration part of the vibration film when not vibrating and the surface of the electrode part. The shape is a combination of at least two of an inclined surface, a curved surface, and a stepped shape whose distance increases from the end toward the center.
With such a configuration, in the pull-type electrostatic transducer in which the electrode is disposed to face only one side of the vibrating membrane, at least a part of the electrode portion of the fixed electrode has an inclined surface, a curved surface, or a stepped shape. The shape is a combination of at least two of them, and the distance between the electrode portion and the surface of the vibrating membrane (the surface during non-vibration) increases from the end portion (end portion of the vibrating portion of the vibrating membrane) toward the center portion. Since the distance is increased, the electrostatic force can be increased while ensuring the amplitude distance of the diaphragm without increasing the voltage applied to the fixed electrode and the diaphragm more than necessary.

The electrostatic transducer according to the present invention is characterized in that an acoustic reflector is provided on the back surface of the electrostatic transducer.
With such a configuration, an acoustic reflector is installed on the back surface of the push-pull electrostatic transducer, and the sound waves emitted from the back surface of the electrostatic transducer are reflected to the front surface. In particular, when an electrostatic transducer is used as an ultrasonic transducer, this acoustic reflector is used to radiate all of the ultrasonic waves radiated from the vent on the back of the ultrasonic transducer to the front of the ultrasonic transducer along the same length path. To be arranged.
Thereby, the sound wave emitted from the back surface of the electrostatic transducer can be effectively used. In particular, when an electrostatic transducer is used as an ultrasonic transducer, ultrasonic waves emitted from the front and back surfaces of the ultrasonic transducer can be effectively used.

In the electrostatic transducer according to the present invention, the acoustic reflector has one end positioned at the center position of the back surface of the electrostatic transducer, and is 45 ° with respect to both sides of the back surface of the electrostatic transducer with the center position as a reference. A pair of first reflectors arranged at an angle and having the other end coincident with an end of the electrostatic transducer, and an angle perpendicular to the ends of the pair of first reflectors. It is characterized by comprising a pair of second reflectors connected in the outer direction of the first reflector and having a length equivalent to the length of the first reflector.
With such a configuration, when an electrostatic transducer is used as an ultrasonic transducer, the acoustic reflector is an ultrasonic transducer in which all the ultrasonic waves radiated from the vent hole on the back surface of the ultrasonic transducer have the same length. Arranged to radiate to the front. That is, the first reflecting plate is disposed at an angle of 45 ° with respect to both sides of the center M on the back surface of the ultrasonic transducer, and the length of the first reflecting plate coincides with the end of the ultrasonic transducer. The ultrasonic wave emitted from the back surface of the ultrasonic transducer is reflected in the horizontal direction by the first reflecting plate. Next, by connecting the second reflecting plate connected at a right angle to the first reflecting plate to the outside of the first reflecting plate, the ultrasonic wave is emitted to the front surface of the ultrasonic transducer. The second reflector length is also required to be equal to the first reflector length. In this way, all the ultrasonic waves radiated from the back surface of the ultrasonic transducer are reflected along the same length path, and all the phases of the ultrasonic waves emitted from the back surface to the front surface are aligned.
Thereby, the ultrasonic wave emitted from the front surface and the back surface of the transducer can be effectively used.

The ultrasonic speaker according to the present invention modulates a carrier wave in an ultrasonic frequency band with a signal wave output from a signal source that generates a signal wave in an audible frequency band, and drives an electrostatic transducer with the modulated wave. An ultrasonic speaker that reproduces a signal sound in an audible frequency band, wherein the electrostatic transducer includes a vibrating membrane having a vibrating electrode layer, a through hole and the vibrating membrane adjacent to the through hole. An electrode having an electrode portion that generates an electrostatic force by an applied voltage, and the electrode is disposed to face the vibrating membrane, and at least a part of the electrode portion is a non-vibrating portion of the vibrating membrane. The distance between the surface at the time of vibration and the surface of the electrode portion is such that the distance increases from the end of the vibrating portion of the vibrating membrane toward the center.
With such a configuration, in an ultrasonic speaker that modulates a carrier wave (carrier wave) in an ultrasonic frequency band with a signal wave in an audible frequency band and drives the electrostatic transducer with the modulated wave, the electrostatic transducer is fixed. At least a part of the electrode portion of the electrode is such that the distance between the electrode portion and the surface of the vibrating membrane (surface during non-vibration) increases from the end portion (end portion of the vibrating portion of the vibrating membrane) toward the center portion. Shape.
Thereby, in the electrostatic transducer used for the ultrasonic speaker, the electrostatic force can be increased while ensuring the amplitude distance of the vibrating membrane. As a result, it is possible to realize an ultrasonic speaker that can generate an acoustic signal having a sufficiently high sound pressure level to obtain a parametric array effect over a wide frequency band.

Further, the speaker device of the present invention includes a signal source that generates a signal wave in an audible frequency band, and an amplifier that amplifies the signal wave output from the signal source, and the electrostatic type is generated by an output signal of the amplifier. A speaker device in which a transducer is driven, wherein the electrostatic transducer is statically driven by a vibration film having a vibration electrode layer, a through-hole, and a voltage applied between the vibration film adjacent to the through-hole. An electrode having an electrode part for generating electric power, wherein the electrode is disposed to face the vibration film, and at least a part of the electrode part is a surface of the vibration part of the vibration film when not vibrating and the electrode The distance from the surface of the electrode portion is such that the distance increases from the end of the vibrating portion of the vibrating membrane toward the central portion.
Thereby, in the electrostatic transducer used in the speaker device, the electrostatic force can be increased while ensuring the amplitude distance of the diaphragm without increasing the voltage applied to the fixed electrode and the diaphragm more than necessary. As a result, an acoustic signal having a high sound pressure level can be generated over a wide frequency band.

Further, the audio signal reproducing method using the electrostatic transducer according to the present invention is configured so that the electrostatic force is generated by the voltage applied between the vibrating membrane having the vibrating electrode layer and the through hole and the vibrating membrane adjacent to the through hole. An electrode having an electrode portion to be generated, wherein the electrode is disposed to face the vibrating membrane, and at least a part of the electrode portion is a surface of the vibrating portion of the vibrating membrane when not vibrating and the electrode portion An electrostatic transducer having a shape in which the distance increases from the end of the vibrating portion of the vibrating membrane toward the central portion at a distance from the surface of the diaphragm, and a signal wave in an audible frequency band is generated by a signal source A procedure, a procedure of generating and outputting a carrier wave in an ultrasonic frequency band by the carrier wave supply means, a procedure of generating a modulation signal obtained by modulating the carrier wave by the signal wave by a modulation means, A step of driving the electrostatic transducer by applying said modulating signal between the vibrating electrode layer of the vibrating film and the serial electrode, characterized in that it comprises a.
In an audio signal reproducing method for an electrostatic transducer including such a procedure, in an ultrasonic speaker that modulates a carrier wave in an ultrasonic frequency band with an audible frequency band signal wave and drives the electrostatic transducer with the modulated wave. The distance between the electrode portion and the surface of the vibrating membrane (the surface during non-vibration) is at least the end portion (the end portion of the vibrating portion of the vibrating membrane). ) From the center to the center.
Thereby, in the electrostatic transducer used for the ultrasonic speaker, the electrostatic force can be increased while ensuring the amplitude distance of the vibrating membrane without increasing the voltage applied to the fixed electrode and the vibrating membrane more than necessary. As a result, it is possible to generate an acoustic signal having a sound pressure level that is sufficiently high to obtain a parametric array effect over a wide frequency band.

Further, the directional acoustic system of the present invention modulates a carrier wave signal in the ultrasonic frequency band with a signal in the first range among audio signals supplied from an acoustic source, and drives an electrostatic transducer with the modulated signal. An ultrasonic speaker that reproduces a signal sound in an audible frequency band; and a bass reproduction speaker that reproduces a signal in a second sound range lower than the first sound range among the sound signals supplied from the acoustic source. The electrostatic transducer of the ultrasonic speaker includes a vibrating membrane having a vibrating electrode layer, a through hole and a voltage applied between the vibrating membrane adjacent to the through hole. An electrode having an electrode part for generating an electrostatic force, wherein the electrode is disposed to face the vibration film, and at least a part of the electrode part is a non-vibration of a vibration part of the vibration film In the distance between the surface and the electrode portion of the surface at, characterized in that the end portion of the vibrating portion of the vibrating film has a shape distance increases toward the central portion.
In the directional acoustic system having the above-described configuration, at least a part of the electrode portion of the fixed electrode portion has a distance between the electrode portion and the surface of the vibrating membrane (the surface at the time of non-vibration) at the end portion (the vibrating portion of the vibrating membrane). An ultrasonic speaker composed of an electrostatic transducer having a shape that increases from the end to the center is used. The ultrasonic speaker reproduces an audio signal in the middle / high range (first range) of the audio signal supplied from the acoustic source. In addition, among the audio signals supplied from the acoustic source, an audio signal in a low sound range (second sound range) is reproduced by a low sound reproduction speaker.
Therefore, in the electrostatic transducer used in the ultrasonic speaker, the electrostatic force can be increased while ensuring the amplitude distance of the diaphragm without increasing the voltage applied to the fixed electrode or the diaphragm more than necessary. As a result, it is possible to reproduce the mid-high range sound so that it can be emitted from a virtual sound source formed in the vicinity of a sound wave reflecting surface such as a screen with sufficient sound pressure and wide band characteristics. Further, since the sound in the low frequency range is directly output from the low sound reproduction speaker provided in the sound system, the low frequency range can be reinforced and a more realistic sound field environment can be created.

The display device of the present invention modulates a carrier wave signal in an ultrasonic frequency band with an audio signal supplied from an acoustic source, and drives an electrostatic transducer with the modulated signal to reproduce a signal sound in an audible frequency band. A display device including an ultrasonic speaker and a projection optical system that projects an image on a projection surface, wherein the electrostatic transducer of the ultrasonic speaker includes a vibration film having a vibration electrode layer, a through hole, An electrode having an electrode part that generates an electrostatic force by a voltage applied between the diaphragm and adjacent to the through-hole, and the electrode is disposed to face the diaphragm, and the electrode part At least part of the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion increases in distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion. Characterized in that it is a that shape.
In the display device having the above configuration, at least a part of the electrode portion of the fixed electrode portion has an end portion (an end portion of the vibrating portion of the vibrating membrane) having a distance between the electrode portion and the surface of the vibrating membrane (the surface when not vibrating). ) Is used as an ultrasonic speaker composed of an electrostatic transducer having a shape that becomes larger toward the center. And the audio | voice signal supplied from an acoustic source is reproduced | regenerated by this ultrasonic speaker.
Thereby, in the electrostatic transducer used for the ultrasonic speaker, the electrostatic force can be increased while ensuring the amplitude distance of the vibrating membrane without increasing the voltage applied to the fixed electrode and the vibrating membrane more than necessary. As a result, an acoustic signal can be reproduced with a sufficient sound pressure and wideband characteristics so as to be emitted from a virtual sound source formed in the vicinity of a sound wave reflecting surface such as a screen. For this reason, it is possible to easily control the reproduction range of the acoustic signal.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

[First Embodiment]
In the electrostatic transducer according to the present invention, at least a part of the electrode portion of the fixed electrode portion (electrostatic force generation surface facing the vibrating portion of the vibrating membrane) is disposed between the electrode portion and the surface of the vibrating membrane (the surface when not vibrating). The distance between the center portion and the center portion is larger than the end portion (the end portion of the vibrating portion of the vibrating membrane). In the present embodiment, the distance between the surface of the vibrating membrane and the electrode portion is increased from the end of the vibrating portion of the vibrating membrane toward the central portion.

  FIG. 1 is a diagram showing the configuration of an electrostatic transducer according to the first embodiment of the present invention. The electrostatic transducer 1 shown in FIG. 1 is a pull-type electrostatic transducer, and is configured by arranging a fixed electrode 20 on one side of a vibrating membrane 22.

  In the electrostatic transducer 1, the distance between the electrode portion 21 of the fixed electrode 20 and the surface of the vibrating membrane 22 (the surface during non-vibration) is at the central portion 26 rather than the end portion 27 of the vibrating portion 25 of the vibrating membrane 22. The shape becomes larger. That is, the distance between the vibrating membrane 22 and the fixed electrode 20 increases from the end portion (small amplitude) 27 of the vibrating portion 25 toward the central portion (large amplitude) 26 of the vibrating portion 25. Specifically, the electrode portion 21 that faces the vibration film 22 and generates an electrostatic force is an inclined surface.

  In the electrostatic transducer 1, the electrostatic force generator 23 and the vent 24 are provided on the fixed electrode 20, so that the electrostatic force generator 23 is designed to have an effective shape for vibrating the vibrating membrane 22. In addition, the vent portion 24 can be effectively designed such that sound pressure is optimally generated by the resonance tube phenomenon. Specifically, the electrostatic force generator 23 is close to a dish shape, and the vent 24 is close to a tube shape.

  When the electrostatic transducer 1 is viewed from the fixed electrode side, circular holes are arranged in a honeycomb shape as shown in FIG. As shown in FIG. 1C, the vibration film 22 has a structure in which a vibration electrode layer (conductive layer) 22A formed of a metal thin film (evaporation) is sandwiched between dielectric films (insulation films) 22B.

  The operation principle of the electrostatic transducer 1 is the same as that of the conventional pull-type electrostatic transducer shown in FIG. 20, and as shown in FIG. 1 (D), the vibrating electrode layer 22A, the fixed electrode 20, In the meantime, a DC bias voltage is applied by the DC bias power source 28, and an AC signal 29 is superimposed on the DC bias voltage and applied from an AC signal source. As a result, electrostatic force acts on the vibrating electrode layer 22A and the electrode portion (inclined surface) 21 of the fixed electrode 20, and the vibrating membrane 22 is driven by the AC signal 29 to vibrate.

  As described above, the electrode portion 21 of the fixed electrode 20 facing the vibrating portion 25 of the vibrating membrane 22 is moved from the end portion (small amplitude) of the vibrating portion 25 toward the central portion (large amplitude) of the vibrating portion 25. The distance between the fixed electrode 20 and the vibrating membrane 22 is made closer to that of the conventional pull-type electrostatic transducer (see FIG. 20) by inclining so that the distance between the vibrating surface and the fixed electrode is increased. Therefore, the electrostatic force can be increased while ensuring the amplitude distance of the diaphragm without increasing the voltage applied to the fixed electrode and the diaphragm more than necessary.

Note that at least a part of the electrode portion 21 of the fixed electrode 20 corresponding to the vibrating portion 25 of the vibrating membrane 22 is directed from the end portion (small amplitude) of the vibrating portion 25 toward the central portion (large amplitude) of the vibrating portion 25. Accordingly, the distance between the vibration surface and the fixed electrode only needs to be increased. Therefore, for example, as shown in FIG. 2A, the electrostatic transducer 2 is replaced with a fixed electrode 31 having an inclined surface 31A and a flat surface 31B. Alternatively, as shown in FIG. 2B, the electrostatic transducer 3 may be composed of a fixed electrode 32 having a convex portion 32A and an inclined surface 32B.
Further, for example, as shown in FIG. 3, the electrostatic transducer 4 may be composed of a fixed electrode in which two or more types of inclined surfaces are combined, such as a fixed electrode 33 having inclined surfaces 33A and 33B having different angles. .

[Second Embodiment]
FIG. 4 is a diagram showing a configuration of an electrostatic transducer according to the second embodiment of the present invention. The electrostatic transducer 5 shown in FIG. 4 has at least a part of an electrode portion (an electrostatic force generation surface facing the vibrating portion 25 of the vibrating membrane) 34A of the fixed electrode 34 corresponding to the vibrating portion 25 of the vibrating membrane 22 The distance between the electrode portion 34A and the surface of the vibrating membrane 22 (the surface during non-vibration) is larger at the center than at the end (the end of the vibrating portion of the vibrating membrane). In the present embodiment, the distance between the surface of the vibrating membrane 22 and the electrode portion 34A is increased from the end of the vibrating portion 25 of the vibrating membrane 22 toward the central portion. Specifically, the electrode portion 34 </ b> A that is the surface of the fixed electrode 34 that faces the vibration film 22 is a concave curved surface.

  As a result, the distance between the fixed electrode 20 and the vibration film 22 can be made shorter than that of a conventional pull-type electrostatic transducer (see FIG. 20), so that a voltage applied to the fixed electrode and the vibration film is more than necessary. The electrostatic force can be increased while ensuring the amplitude distance of the vibration film without increasing it.

  Note that at least a part of the fixed electrode 34 facing the vibration surface of the vibration film 22 moves from the end portion (the amplitude is small) of the vibration portion 25 toward the center portion (the amplitude is large) of the vibration portion 25. Since the distance between the surface and the fixed electrode 34 only needs to be large, for example, as shown in FIG. 5, the electrostatic transducer 6 may be composed of a fixed electrode 35 having a curved surface 35A and a flat surface 35B. Further, as shown in FIG. 6, the electrostatic transducer 7 may be constituted by a fixed electrode 36 having a convex curved surface 36A.

[Third Embodiment]
FIG. 7 is a diagram showing the configuration of an electrostatic transducer according to the third embodiment of the present invention. In the electrostatic transducer 8 shown in FIG. 7, two steps are provided on the electrode portion (electrostatic force generation surface) of the fixed electrode 37.

  Accordingly, the electrode portion (electrostatic force generation surface) of the fixed electrode 37 can be brought closer to the vibration film 22 as compared with a conventional pull-type electrostatic transducer (see FIG. 20). The electrostatic force can be increased while securing the amplitude distance of the diaphragm without increasing the voltage applied to the unnecessarily.

  Further, as shown in FIG. 8, the electrostatic transducer 9 may be constituted by a fixed electrode 38 having three or more steps.

[Fourth Embodiment]
FIG. 9 is a diagram showing a configuration of an electrostatic transducer according to the fourth embodiment of the present invention. In the electrostatic transducer 10 shown in FIG. 9, a curved surface 39 </ b> A and an inclined surface 39 </ b> B are provided on the electrode portion of the fixed electrode 39 (an electrostatic force generation surface facing the vibration film).

  The electrostatic transducer 10 shown in FIG. 9 is a combination of the shape (slope) of the fixed electrode of the first embodiment and the shape (curved surface) of the second embodiment. As described above, it is possible to freely combine the shapes of the slopes, curved surfaces, and steps used in the fixed electrodes in the first to third embodiments.

[Fifth Embodiment]
In the fixed electrodes shown in the first to fourth embodiments, the shape of the embodiment can be created by, for example, cutting a metal material, but the metal is attached to the insulating material (plating). Changes can be made without departing from the gist of the present invention even if the treatment and the conductive paste are applied.

  For example, like the fixed electrode 40 of the electrostatic transducer 11 shown in FIG. 10, the structure which apply | coats the electrically conductive paste 40B on the board | plate of the fixed electrode base material 40A formed with the insulating material may be sufficient. Thereby, a fixed electrode can be reduced in weight.

[Sixth Embodiment]
FIG. 11 is a diagram showing a configuration of an electrostatic transducer according to the sixth embodiment of the present invention. The structure of the fixed electrode is not limited to metal, and even if it has an insulating material in part, it can be changed without departing from the gist of the present invention. For example, as a modification of the electrostatic transducer 3 shown in FIG. 2B, an insulating film 41A (epoxy resin) is provided between the vibration film 22 and the fixed electrode 41 as in the electrostatic transducer 12 shown in FIG. An insulating material such as

[Seventh Embodiment]
FIG. 12 is a diagram showing the configuration of an electrostatic transducer according to the seventh embodiment of the present invention. In the first to sixth embodiments, the configuration of the pull-type electrostatic transducer in which the fixed electrode is disposed only on one side of the vibration film has been described. However, the fixed electrode is disposed on both sides of the vibration film. Even in the configuration of the push-pull type electrostatic transducer, the structure of the electrodes can be considered in the same manner as that of the pull-type electrostatic transducer only by being disposed facing each other.

  For example, the push-pull type electrostatic transducer 13 shown in FIG. In this electrostatic transducer 13, the front side fixed electrode 20A and the back side fixed electrode 20B are arranged so as to sandwich the vibration film 22, and the electrodes facing the vibration film 22 of the fixed electrodes 20A and 20B. The portions 21A and 21B are inclined surfaces.

The operation principle of this push-pull type electrostatic transducer 13 is the same as that of the conventional push-pull type electrostatic transducer shown in FIG. 21, and as shown in FIG. A DC bias voltage is applied to a vibrating electrode layer 22A (not shown) of the vibrating membrane 22, and AC signals 29A and 29B are applied to the fixed electrodes 20A and 20B. With the above configuration, the AC signals 29A and 29B having the same amplitude and inverted phases are applied to the front fixed electrode 20A and the rear fixed electrode 20B with reference to the center tap. As a result, an electrostatic force acts between the vibrating electrode layer 22A (not shown) of the vibrating membrane 22 and the electrode portions 21A and 21B facing the vibrating membranes of the fixed electrodes 20A and 20B, and the vibrating membrane 22 causes the AC signal 29A. , 29B to vibrate.
The configuration of this circuit is an example, and can be changed without departing from the gist of the present invention.

  Note that, like the electrostatic transducer 14 shown in FIG. 13, a fixed electrode 37 (see FIG. 7) and a fixed electrode 32 (see FIG. 2B) having different shapes can be used, and the vibrating membrane 22 can be used. The pair of fixed electrodes facing each other does not necessarily have the same shape.

  As described above, in the conventional electrostatic transducer, the distance between the fixed electrode and the vibrating membrane is a flat surface in a state where the vibrating membrane does not vibrate. However, in the electrostatic transducer of the present invention, The distance between the fixed electrode and the vibrating membrane is not set at a constant interval in accordance with the vibration of the membrane. As a result, the distance between the fixed electrode and the diaphragm can be reduced, so that the electrostatic force can be increased while securing the amplitude distance of the diaphragm without increasing the voltage applied to the fixed electrode or the diaphragm more than necessary. .

[Eighth Embodiment]
Next, FIG. 14 shows a configuration example of an electrostatic transducer according to the eighth embodiment of the present invention. The configuration of the electrostatic transducer 15 shown in FIG. 14 is the same as the configuration of the push-pull type electrostatic transducer 13 shown in FIG. 12 except that the acoustic reflectors 101 and 102 are installed on the back surface of the electrostatic transducer. Are the same. The electrostatic transducer 15 including the acoustic reflectors 101 and 102 is particularly effective when driven by a modulation signal obtained by modulating a carrier wave in an ultrasonic frequency band with an audible frequency band signal. It is.

Hereinafter, a case where the electrostatic transducer 15 is used as an ultrasonic transducer will be described.
In FIG. 14, the acoustic reflectors 101 and 102 are placed on the front surface of the electrostatic transducer 15 through a path having the same length of all the ultrasonic waves radiated from the vent portion 24B of the fixed electrode 20B on the back surface side of the electrostatic transducer 15. It is arranged to be emitted.
That is, one end of the acoustic reflector is located at the center position M of the back surface of the electrostatic transducer 15 and is disposed at an angle of 45 ° with respect to both sides of the back surface of the electrostatic transducer 15 with respect to the center position. The pair of first reflecting plates 101 and 101 whose ends coincide with the end portions X1 and X2 of the electrostatic transducer 15 and an angle perpendicular to the ends of the pair of first reflecting plates 101 and 101 are set at right angles. A pair of second reflectors 102 and 102 each having a length equivalent to the length of the first reflector are connected to the outside of the first reflector.

  In the above configuration, the first reflectors 101 and 101 are disposed at an angle of 45 ° with respect to both sides of the center M on the back surface of the electrostatic transducer 15, and the end of the first reflector 101 coincides with the end of the electrostatic transducer 15. The length of is required. The ultrasonic waves emitted from the back surface of the electrostatic transducer 15 by the first reflectors 101 and 101 are reflected in the horizontal direction.

  Next, by connecting the second reflectors 102 and 102 connected at a right angle to the first reflectors 101 and 101 to the outside of the first reflectors 101 and 101, respectively, the ultrasonic waves are electrostatically discharged. Released to the front of the mold transducer 15. The second reflector length is also required to be equal to the first reflector length. What is important here is that all the ultrasonic waves radiated from the back surface of the electrostatic transducer 15 have the same length path. This is because the same path length means that the phases of the ultrasonic waves emitted from the back surface are all aligned.

  Further, the reason why the sound wave can be handled geometrically as shown in FIG. 14 is that the sound wave to be emitted is an ultrasonic wave and therefore has a very strong directivity. Another point that needs to be mentioned is the time difference between the ultrasonic wave emitted from the front surface of the electrostatic transducer 15 and the ultrasonic wave reflected from the rear surface and emitted to the front surface.

The ultrasonic wave emitted from a point a distance away from the center of the transducer is assumed to be circular and its radius is r, and the distance to reach the transducer front surface is approximately 2r, that is, the diameter of the transducer. Of course, the distance a must satisfy the following equation.
0 ≦ a ≦ r (1)

Now, assuming that the transducer diameter is about 10 cm and the sound velocity is 340 m / sec, the time difference between the ultrasonic wave emitted from the front surface and the ultrasonic wave emitted from the back surface and reaching the front surface is about 0.29 msec. There is no problem because it is a time difference that humans cannot perceive. That is, ultrasonic waves emitted from the front and back surfaces of the transducer can be used effectively.
The arrangement and shape of the acoustic reflector are merely examples, and can be changed without departing from the gist of the present invention.

[Ninth Embodiment]
Next, an ultrasonic speaker and speaker device according to a ninth embodiment of the present invention will be described. FIG. 15A is a diagram showing a configuration of an ultrasonic speaker using the electrostatic transducer of the present invention. The ultrasonic speaker according to this embodiment uses the above-described electrostatic transducer of the present invention (the electrostatic transducer shown in FIGS. 1 to 14). In this electrostatic transducer, the distance between the surface of the electrode portion of the fixed electrode (electrostatic force generation surface facing the vibrating portion of the vibrating membrane) and the surface of the vibrating portion of the vibrating membrane is from the end of the vibrating portion of the vibrating membrane. It is comprised so that it may become large as it goes to the center part. Thereby, the electrostatic force can be increased while ensuring the amplitude distance of the diaphragm without increasing the voltage applied to the fixed electrode and the diaphragm more than necessary. For this reason, the ultrasonic speaker which can generate | occur | produce the acoustic signal of a sufficiently high sound pressure level is realizable.

In FIG. 15A, an ultrasonic speaker 16 includes an audio frequency wave oscillation source 201 that generates a signal wave in an audio frequency band, and a carrier wave oscillation that generates and outputs an ultrasonic frequency carrier wave (carrier wave). A source 202, a modulator 203, a power amplifier 204, and an electrostatic transducer 205A are included.
The modulator 203 modulates the carrier wave output from the carrier wave oscillation source 202 with the signal wave in the audible frequency band output from the audio frequency wave oscillation source 201, and transmits the modulated wave to the electrostatic transducer 205A via the power amplifier 204. Supply.

  In the above configuration, the carrier wave in the ultrasonic frequency band output from the carrier wave oscillation source 202 by the signal wave output from the audible frequency wave oscillation source 201 is modulated by the modulator 203 and the modulated signal amplified by the power amplifier 204 is used. The electrostatic transducer 205A is driven. As a result, the modulated signal is converted into a sound wave of a finite amplitude level by the electrostatic transducer 205A, and this sound wave is radiated into the medium (in the air) and the signal in the original audible frequency band due to the nonlinear effect of the medium (air). The sound is self-playing.

  In other words, sound waves are coarse and dense waves that propagate using air as a medium, so that in the process of modulated ultrasonic waves, the dense and sparse portions of air appear prominently, and the dense portions have high sound speed and sparseness. Since the sound speed of such a portion is slow, the modulation wave itself is distorted. As a result, the waveform is separated into a carrier wave (ultrasonic frequency band), and a signal wave (signal sound) in an audible frequency band is reproduced.

Ultrasound is strongly attenuated in the air and attenuates in proportion to the square of its frequency. Therefore, when the carrier frequency (ultrasonic wave) is low, it is possible to provide an ultrasonic speaker in which the sound reaches far as a beam with little attenuation.
On the contrary, if the carrier frequency is high, the attenuation is severe, so that the parametric array effect does not occur sufficiently and an ultrasonic speaker in which the sound spreads can be provided. These are very effective functions because the same ultrasonic speaker can be used according to the application.

  Also, dogs who often live with humans as pets can listen to sounds up to 40 kHz, and cats can listen to sounds up to 100 kHz, so if you use a carrier frequency higher than that, there will be no effect on the pet. There are also advantages. In any case, the fact that it can be used at various frequencies brings many advantages.

  The electrostatic transducer of the present invention can be used not only as an ultrasonic speaker but also as a normal speaker device. For example, as shown in FIG. 15B, the electrostatic transducer 205B is driven by a signal obtained by amplifying the signal wave output from the audible frequency wave oscillation source 201 by the power amplifier 204.

  As described above, the ultrasonic speaker system and the speaker device of the present invention use the electrostatic transducer of the present invention, and can reproduce an acoustic signal with a sufficient sound pressure level and wide band characteristics. it can. In particular, in an ultrasonic speaker, an acoustic signal can be reproduced so as to be emitted from a virtual sound source formed in the vicinity of a sound wave reflecting surface such as a screen with a sufficient sound pressure level and wide band characteristics. For this reason, the reproduction range can be easily controlled.

[Tenth embodiment]
Next, the electrostatic transducer according to the present invention, that is, the surface of the electrode portion of the fixed electrode (surface of electrostatic force generation facing the vibrating portion of the vibrating membrane) and the surface of the vibrating portion of the vibrating membrane (surface during non-vibration) The distance is increased as it goes from the end of the vibrating portion of the vibrating membrane to the center portion, while ensuring the amplitude distance of the vibrating membrane without increasing the voltage applied to the fixed electrode and the vibrating membrane more than necessary. A directional acoustic system using an ultrasonic speaker composed of an electrostatic transducer capable of increasing electrostatic force will be described.

The example shown here is an example in which a push-pull type electrostatic transducer (see FIG. 12) having better sound quality (less distortion) than a pull type electrostatic transducer (see FIG. 1) is used. However, of course, a pull-type electrostatic transducer may be used.
The electrostatic transducer driven by a signal in the ultrasonic frequency band is hereinafter also referred to as “ultrasonic transducer”.

  Hereinafter, a projector (display device) will be described as an example of a directional acoustic system according to the present invention. FIG. 16 shows the usage state of the projector according to the present invention. As shown in the figure, the projector 301 is installed behind the viewer 303, projects an image on a screen 302 installed in front of the viewer 303, and uses the ultrasonic speaker mounted on the projector 301 to screen 302. A virtual sound source is formed on the projection plane and the sound is reproduced.

An appearance configuration of the projector 301 is shown in FIG. The projector 301 includes a projector main body 320 including a projection optical system that projects an image on a projection surface such as a screen, and ultrasonic transducers 324A and 324B that can oscillate sound waves in an ultrasonic frequency band, and is supplied from an acoustic source. And an ultrasonic speaker that reproduces a signal sound in an audible frequency band from a sound signal. In the present embodiment, in order to reproduce a stereo audio signal, ultrasonic transducers 324A and 324B constituting ultrasonic speakers are mounted on the left and right with a projector lens 331 constituting a projection optical system interposed therebetween in the projector body.
Further, a low-pitched sound reproduction speaker 323 is provided on the bottom surface of the projector main body 320. Reference numeral 325 denotes a height adjusting screw for adjusting the height of the projector main body 320, and reference numeral 326 denotes an exhaust port for the air cooling fan.

  In the projector 301, the electrostatic transducer of the present invention is used as the ultrasonic transducers 324A and 324B constituting the ultrasonic speaker. In this electrostatic transducer, the distance between the surface of the electrode portion of the fixed electrode (electrostatic force generation surface facing the vibrating portion of the vibrating membrane) and the surface of the vibrating portion of the vibrating membrane (the surface when not vibrating) is Since the distance is greater at the center than at the end of the vibration part, and the electrostatic force can be increased while ensuring the amplitude distance of the diaphragm, the sound with a sufficiently high sound pressure level A signal can be generated. For this reason, by conventionally changing the frequency of the carrier wave to control the spatial reproduction range of the reproduction signal in the audible frequency band, an acoustic effect that can be obtained in a stereo surround system or 5.1ch surround system is conventionally required. Thus, it is possible to realize a projector that can be realized without requiring a large-scale sound system and is easy to carry.

  Next, an electrical configuration of the projector 301 is shown in FIG. The projector 301 includes an operation input unit 310, a reproduction range setting unit 312, a reproduction range control processing unit 313, an audio / video signal reproduction unit 314, a carrier wave oscillation source 316, modulators 318A and 318B, power amplifiers 322A and 322B, and a super It has an ultrasonic speaker comprising sound wave transducers 324A and 324B, a high-pass filter 317A and 317B, a low-pass filter 319, a mixer 321, a power amplifier 322C, a low-frequency sound reproduction speaker 323, and a projector main body 320.

  The projector main body 320 includes a video generation unit 332 that generates a video and a projection optical system 333 that projects the generated video on a projection surface. The projector 301 is configured by integrating an ultrasonic speaker and a bass reproduction speaker 323 and a projector main body 320.

  The operation input unit 310 has various function keys including a numeric keypad, numeric keys, and a power key for turning the power on and off. The reproduction range setting unit 312 can input data specifying a reproduction range of a reproduction signal (signal sound) by a user operating the operation input unit 310 with a key. The frequency of the carrier wave that defines the reproduction range of the signal is set and held. The reproduction range of the reproduction signal is set by designating a distance that the reproduction signal reaches in the radial axis direction from the sound wave emission surfaces of the ultrasonic transducers 324A and 324B.

Also, the reproduction range setting unit 312 can set the frequency of the carrier wave by the control signal output from the audio / video signal reproduction unit 314 according to the video content.
Further, the reproduction range control processing unit 313 refers to the setting contents of the reproduction range setting unit 312 and changes the frequency of the carrier wave generated by the carrier wave oscillation source 316 so as to be within the set reproduction range. It has a function of controlling the oscillation source 316.
For example, when the distance corresponding to the carrier wave frequency of 50 kHz is set as the internal information of the reproduction range setting unit 312, the carrier wave oscillation source 316 is controlled to oscillate at 50 kHz.

The reproduction range control processing unit 313 stores in advance a table indicating the relationship between the distance that the reproduction signal reaches in the radial axis direction from the sound wave emitting surfaces of the ultrasonic transducers 324A and 324B that define the reproduction range and the frequency of the carrier wave. It has a storage part. The data in this table is obtained by actually measuring the relationship between the frequency of the carrier wave and the reach distance of the reproduction signal.
The reproduction range control processing unit 313 obtains the frequency of the carrier wave corresponding to the distance information set with reference to the table based on the setting content of the reproduction range setting unit 312 and oscillates the carrier wave so as to be the frequency. Control the source 316.

The audio / video signal reproduction unit 314 is, for example, a DVD player that uses a DVD as a video medium. Among the reproduced audio signals, the R channel audio signal is sent to the modulator 318A via the high-pass filter 317A. The signal is output to the modulator 318B via the high-pass filter 317B, and the video signal is output to the video generation unit 332 of the projector main body 320.
The R channel audio signal and the L channel audio signal output from the audio / video signal reproduction unit 314 are combined by the mixer 321 and input to the power amplifier 322C via the low-pass filter 319. . The audio / video signal reproduction unit 314 corresponds to an acoustic source.

The high-pass filters 317A and 317B have a characteristic of passing only the frequency components in the middle and high sound range (first sound range) in the R channel and L channel audio signals, respectively. Only the low frequency range (second range) frequency component of the audio signal of the channel is passed.
Accordingly, among the R channel and L channel audio signals, the mid and high range audio signals are reproduced by the ultrasonic transducers 324A and 324B, respectively, and among the R channel and L channel audio signals, the low range audio signals are low frequencies. It is reproduced by the reproduction speaker 323.

  The audio / video signal reproduction unit 314 is not limited to a DVD player, and may be a reproduction device that reproduces a video signal input from the outside. In addition, the audio / video signal reproduction unit 314 instructs the reproduction range setting unit 312 to dynamically change the reproduction range of the reproduced sound in order to produce an acoustic effect corresponding to the reproduced video scene. Has a function of outputting a control signal.

The carrier wave oscillation source 316 has a function of generating a carrier wave having a frequency in the ultrasonic frequency band designated by the reproduction range setting unit 312 and outputting the carrier wave to the modulators 318A and 318B.
The modulators 318A and 318B AM modulate the carrier wave supplied from the carrier wave oscillation source 316 with the audio signal in the audible frequency band output from the audio / video signal reproduction unit 314, and each of the modulated signals is a power amplifier 322A. , 322B.

  The ultrasonic transducers 324A and 324B are driven by modulation signals output from the modulators 318A and 318B via the power amplifiers 322A and 322B, respectively, and convert the modulation signals into sound waves of a finite amplitude level and radiate them into the medium. And has a function of reproducing a signal sound (reproduction signal) in an audible frequency band.

The video generation unit 332 includes a display such as a liquid crystal display and a plasma display panel (PDP), a drive circuit that drives the display based on a video signal output from the audio / video signal reproduction unit 314, and the like. A video obtained from the video signal output from the audio / video signal reproduction unit 314 is generated.
The projection optical system 333 has a function of projecting an image displayed on the display onto a projection surface such as a screen installed in front of the projector main body 320.

  Next, the operation of the projector 301 having the above configuration will be described. First, data (distance information) instructing the reproduction range of the reproduction signal is set in the reproduction range setting unit 312 from the operation input unit 310 by the user's key operation, and a reproduction instruction is given to the audio / video signal reproduction unit 314.

As a result, distance information defining the reproduction range is set in the reproduction range setting unit 312, and the reproduction range control processing unit 313 takes in the distance information set in the reproduction range setting unit 312 and stores it in the built-in storage unit. The carrier wave oscillation source 316 is controlled so as to obtain the frequency of the carrier wave corresponding to the set distance information with reference to the set table and to generate the carrier wave of the frequency.
As a result, the carrier wave oscillation source 316 generates a carrier wave having a frequency corresponding to the distance information set in the reproduction range setting unit 312 and outputs the carrier wave to the modulators 318A and 318B.

  On the other hand, the audio / video signal reproduction unit 314 outputs the R channel audio signal of the reproduced audio signal to the modulator 318A via the high pass filter 317A, and the L channel audio signal to the modulator 318B via the high pass filter 317B. In addition, the R channel audio signal and the L channel audio signal are output to the mixer 321, and the video signal is output to the video generation unit 332 of the projector main body 320.

Therefore, the high-pass filter 317A inputs the mid-high range audio signal of the R channel audio signal to the modulator 318, and the high-pass filter 317B converts the mid-high range audio signal of the L channel audio signal to the modulator 318B. Is input.
The R channel audio signal and the L channel audio signal are synthesized by the mixer 321, and the low frequency audio signal of the R channel audio signal and the L channel audio signal is input to the power amplifier 322 C by the low pass filter 319. Is done.

The video generation unit 332 generates a video by driving the display based on the input video signal, and displays the video. The image displayed on the display is projected onto a projection surface, for example, the screen 302 shown in FIG. 16 by the projection optical system 333.
On the other hand, the modulator 318A AM-modulates the carrier wave output from the carrier wave oscillation source 316 with the mid-high range audio signal in the R channel audio signal output from the high-pass filter 317A, and outputs the result to the power amplifier 322A. .
Further, the modulator 318B AM-modulates the carrier wave output from the carrier wave oscillation source 316 with the mid-high range audio signal in the L channel audio signal output from the high pass filter 317B, and outputs the result to the power amplifier 322B. .

The modulation signals amplified by the power amplifiers 322A and 322B are applied to the ultrasonic transducers 324A and 324B, respectively, and the modulation signals are converted into sound waves (acoustic signals) of a finite amplitude level and radiated to the medium (in the air). Then, the ultrasonic transducer 324A reproduces the mid-high range audio signal in the R channel audio signal, and the ultrasonic transducer 324B reproduces the mid-high range audio signal in the L channel audio signal. .
Also, the low-frequency audio signals in the R channel and L channel amplified by the power amplifier 322C are reproduced by the low tone reproduction speaker 323.

  As described above, in the propagation of ultrasonic waves radiated into the medium (in the air) by the ultrasonic transducer, the sound speed increases at a portion where the sound pressure is high and the sound speed is slow at a portion where the sound pressure is low. Become. As a result, waveform distortion occurs.

  When a signal (carrier wave) in the radiated ultrasonic band is modulated (AM modulation) with a signal in the audible frequency band, the signal wave in the audible frequency band used for modulation is super It is formed so as to be self-demodulated separately from the carrier wave in the sonic frequency band. At this time, the spread of the reproduction signal becomes a beam shape due to the characteristics of ultrasonic waves, and the sound is reproduced only in a specific direction completely different from that of a normal speaker.

  The beam-like reproduction signal output from the ultrasonic transducer 324 constituting the ultrasonic speaker is radiated toward the projection surface (screen) on which the image is projected by the projection optical system 333, and is reflected and diffused by the projection surface. In this case, until the reproduction signal is separated from the carrier wave in the radial axis direction (normal direction) from the sound wave emitting surface of the ultrasonic transducer 324 according to the frequency of the carrier wave set in the reproduction range setting unit 312. And the beam width (beam divergence angle) of the carrier wave are different, the reproduction range changes.

  FIG. 19 shows a state when a reproduction signal is reproduced by an ultrasonic speaker including the ultrasonic transducers 324A and 324B in the projector 301. In the projector 301, when the ultrasonic transducer is driven by the modulation signal obtained by modulating the carrier wave with the audio signal, if the carrier frequency set by the reproduction range setting unit 312 is low, the sound wave emitting surface of the ultrasonic transducer 324 To the direction of the radiation axis (the distance until the reproduction signal is separated from the carrier wave in the normal direction of the sound wave radiation surface, that is, the distance to the reproduction point becomes long.

Therefore, the reproduced beam of the reproduced signal in the audible frequency band reaches the projection plane (screen) 302 without being relatively expanded, and is reflected on the projection plane 302 in this state. Therefore, the reproduction range is as shown in FIG. Becomes a audible range A indicated by a dotted arrow, and a reproduction signal (reproduced sound) can be heard only in a relatively narrow and narrow range from the projection plane 302.

  On the other hand, when the carrier frequency set by the reproduction range setting unit 312 is higher than the case described above, the sound wave radiated from the sound wave emission surface of the ultrasonic transducer 324 is narrower than when the carrier frequency is low. However, the distance until the reproduction signal is separated from the carrier wave in the radial direction (normal direction of the acoustic wave emission surface) from the sound wave emission surface of the ultrasonic transducer 324, that is, the distance to the reproduction point is shortened.

  Therefore, the reproduced reproduction signal beam in the audible frequency band spreads before reaching the projection plane 302 and reaches the projection plane 302, and is reflected on the projection plane 302 in this state. 19, an audible range B indicated by a solid arrow is obtained, and a playback signal (playback sound) can be heard only in a relatively close and wide range from the projection plane 302.

  As described above, in the projector of the present invention, the electrostatic transducer of the present invention is used as the ultrasonic transducer constituting the ultrasonic speaker, and the voltage applied to the fixed electrode and the diaphragm is increased more than necessary. Since the electrostatic force can be increased while ensuring the amplitude distance of the diaphragm, the acoustic signal can be emitted from a virtual sound source formed near the sound wave reflecting surface such as a screen with sufficient sound pressure level and wide band characteristics. Can be played back. For this reason, the reproduction range can be easily controlled.

  The projector described above is used for viewing images on a large screen. Recently, large-screen liquid crystal televisions and large-screen plasma televisions are rapidly spreading, and those large-screen televisions are also used. The ultrasonic speaker of the present invention can be used effectively.

  That is, by using the ultrasonic speaker according to the present invention for a large screen television, it becomes possible to radiate an audio signal locally toward the front of the large screen television.

  Although the embodiments of the present invention have been described above, the electrostatic transducer, the ultrasonic speaker, and the display device of the present invention are not limited to the illustrated examples described above, and do not depart from the gist of the present invention. Of course, various changes can be made within the range.

The block diagram of the electrostatic transducer concerning the 1st Embodiment of this invention. The figure which shows the modification of the electrostatic transducer shown in FIG. The figure which shows the other modification of the electrostatic type transducer shown in FIG. The block diagram of the electrostatic transducer concerning the 2nd Embodiment of this invention. The figure which shows the modification of the electrostatic transducer shown in FIG. The figure which shows the other modification of the electrostatic type transducer shown in FIG. The block diagram of the electrostatic transducer concerning the 3rd Embodiment of this invention. The figure which shows the modification of the electrostatic transducer shown in FIG. The block diagram of the electrostatic transducer concerning the 4th Embodiment of this invention. The block diagram of the electrostatic transducer concerning the 5th Embodiment of this invention. The block diagram of the electrostatic transducer concerning the 6th Embodiment of this invention. The block diagram of the electrostatic transducer concerning the 7th Embodiment of this invention. The figure which shows the modification of the electrostatic transducer shown in FIG. The figure which shows the example which provided the reflecting plate in the back surface of the electrostatic transducer. The figure which shows the structure of the ultrasonic speaker by this invention, and a speaker apparatus. The figure which shows the use condition of the projector by this invention. FIG. 17 is a diagram showing an external configuration of the projector shown in FIG. 16. FIG. 17 is a block diagram showing an electrical configuration of the projector shown in FIG. 16. Explanatory drawing of the reproduction | regeneration state of the reproduction signal by an ultrasonic transducer. The figure which shows the structure of the conventional pull type electrostatic transducer. The figure which shows the structure of the conventional push pull type electrostatic transducer. Explanatory drawing of the problem of the conventional electrostatic transducer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1-15 ... Electrostatic transducer, 16 ... Ultrasonic speaker, 17 ... Speaker apparatus, 20 ... Fixed electrode, 20A ... Front side fixed electrode, 20B ... Back side fixed electrode , 21, 21A, 21B ... electrode part, 22 ... vibrating membrane, 22A ... vibrating electrode layer, 22B ... dielectric film, 23 ... electrostatic force generating part, 24, 24A ... Ventilation hole part, 25 ... vibration part, 28 ... DC bias power supply, 29, 29A, 29B ... AC signal, 31-41 ... fixed electrode, 40A ... fixed electrode base material, 40B .. Conductive paste, 101, 102 ... acoustic reflector, 201 ... audible frequency wave oscillation source, 202 ... carrier wave oscillation source, 203 ... modulator, 204 ... power amplifier, 205A, 205B ... Electrostatic transducer, 301 ... Professional 302 ... screen (projection plane), 303 ... viewer, 310 ... operation input unit, 312 ... reproduction range setting unit, 313 ... reproduction range control processing unit, 314 ... Audio / video signal reproduction unit, 316, carrier wave oscillation source, 317A, 317B, high pass filter, 318A, 318B, modulator, 319, low pass filter, 320, projector main body, 321, ..Mixer, 322A, 322B ... Power amplifier, 322C ... Power amplifier, 323 ... Low-frequency speaker, 324, 324A, 324B ... Ultrasonic transducer, 331 ... Projector lens, 332 ..Image generation unit, 333 ... Projection optical system

Claims (22)

A vibrating membrane having a vibrating electrode layer;
An electrode having an electrode portion that generates an electrostatic force by a voltage applied between the through hole and the vibrating membrane adjacent to the through hole;
Including
The electrode is disposed opposite the vibrating membrane;
At least a part of the electrode part is at a distance in the center part at a distance between a surface of the vibrating part of the vibrating film when not vibrating and a surface of the electrode part at a center part than at an end part of the vibrating part of the vibrating film. An electrostatic transducer characterized by having a large shape. At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. The electrostatic transducer according to claim 1, wherein the electrostatic transducer has a shape of an inclined surface. At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. The electrostatic transducer according to claim 1, wherein the electrostatic transducer has a curved shape. At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. The electrostatic transducer according to claim 1, wherein the electrostatic transducer has a stepped shape. At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. The electrostatic transducer according to claim 1, wherein the electrostatic transducer has a shape obtained by combining at least two of an inclined surface, a curved surface, and a stepped shape. A vibrating membrane having a vibrating electrode layer;
A first electrode having an electrode portion for generating an electrostatic force by a voltage applied between the through-hole and the through-hole adjacent to the through-hole, and the through-hole and the vibrating membrane adjacent to the through-hole. A second electrode having an electrode part for generating an electrostatic force by a voltage applied between
Including
The first electrode and the second electrode are disposed to face both surfaces of the vibrating membrane, respectively.
At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. An electrostatic transducer characterized by the following shape. At least a part of the electrode portion has a larger distance from the end of the vibrating portion of the front vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. The electrostatic transducer according to claim 6, wherein the electrostatic transducer has a shape of an inclined surface. At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. The electrostatic transducer according to claim 6, wherein the electrostatic transducer has a curved shape. At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. The electrostatic transducer according to claim 6, wherein the electrostatic transducer has a stepped shape. At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. The electrostatic transducer according to claim 6, which is a combination of at least two of an inclined surface, a curved surface, and a stepped shape. A vibrating membrane having a vibrating electrode layer;
An electrode having an electrode portion that generates an electrostatic force by a voltage applied between the through hole and the vibrating membrane adjacent to the through hole;
Including
The electrode is disposed to face only one side of the vibrating membrane,
At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. An electrostatic transducer characterized by the following shape. At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. The electrostatic transducer according to claim 11, wherein the electrostatic transducer has a shape of an inclined surface. At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. The electrostatic transducer according to claim 11, wherein the electrostatic transducer has a curved shape. At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. The electrostatic transducer according to claim 11, wherein the electrostatic transducer has a stepped shape. At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. The electrostatic transducer according to claim 11, wherein the electrostatic transducer has a combination of at least two of an inclined surface, a curved surface, and a stepped shape. The electrostatic transducer according to claim 6, wherein an acoustic reflector is provided on a back surface of the electrostatic transducer. One end of the acoustic reflector is located at the center position of the back surface of the electrostatic transducer, and is disposed at an angle of 45 ° with respect to both sides of the back surface of the electrostatic transducer with respect to the center position. A pair of first reflectors of a length matching the end of
A pair of second layers having a length equal to the length of the first reflector plate connected to the outside of the first reflector plate at an angle perpendicular to the end portions of the pair of first reflector plates. The electrostatic transducer according to claim 16, comprising: a reflector. A carrier wave in the ultrasonic frequency band is modulated by a signal wave output from a signal source that generates a signal wave in the audible frequency band, and an acoustic transducer is driven by the modulated wave to reproduce a signal sound in the audible frequency band. An ultrasonic speaker,
The electrostatic transducer is
A vibrating membrane having a vibrating electrode layer;
An electrode having an electrode portion that generates an electrostatic force by a voltage applied between the through hole and the vibrating membrane adjacent to the through hole;
Including
The electrode is disposed opposite the vibrating membrane;
At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. An ultrasonic speaker characterized by the following shape. The speaker device includes a signal source that generates a signal wave in an audible frequency band and an amplifier that amplifies the signal wave output from the signal source, and the electrostatic transducer is driven by the output signal of the amplifier. And
The electrostatic transducer is
A vibrating membrane having a vibrating electrode layer;
An electrode having an electrode portion that generates an electrostatic force by a voltage applied between the through hole and the vibrating membrane adjacent to the through hole;
Including
The electrode is disposed opposite the vibrating membrane;
At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. The speaker device characterized by the following. A vibrating membrane having a vibrating electrode layer;
An electrode having an electrode portion that generates an electrostatic force by a voltage applied between the through hole and the vibrating membrane adjacent to the through hole;
Including
The electrode is disposed opposite the vibrating membrane;
At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. While using an electrostatic transducer that has the shape
Generating a signal wave of an audible frequency band by a signal source;
A procedure for generating and outputting a carrier wave in an ultrasonic frequency band by the carrier wave supply means,
A procedure for generating a modulated signal obtained by modulating a carrier wave with the signal wave by a modulating means;
A procedure for driving an electrostatic transducer by applying the modulation signal between the electrode and the vibrating electrode layer of the vibrating membrane;
A method for reproducing an audio signal using an electrostatic transducer. An ultrasonic wave that modulates a carrier wave signal in an ultrasonic frequency band by a signal in the first sound range among audio signals supplied from an acoustic source, and drives an electrostatic transducer by the modulated signal to reproduce a signal sound in an audible frequency band Speakers,
A low-frequency sound reproduction speaker for reproducing a signal in a second sound range lower than the first sound range among the sound signals supplied from the acoustic source;
A directional acoustic system comprising:
The electrostatic transducer of the ultrasonic speaker is
A vibrating membrane having a vibrating electrode layer;
An electrode having an electrode portion that generates an electrostatic force by a voltage applied between the through hole and the vibrating membrane adjacent to the through hole;
Including
The electrode is disposed opposite the vibrating membrane;
At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. A directional acoustic system characterized by An ultrasonic speaker that modulates a carrier wave signal in an ultrasonic frequency band with an audio signal supplied from an acoustic source, and reproduces an audible frequency band signal sound by driving an electrostatic transducer with the modulated signal;
A projection optical system that projects an image onto a projection surface;
A display device comprising:
The electrostatic transducer of the ultrasonic speaker is
A vibrating membrane having a vibrating electrode layer;
An electrode having an electrode portion that generates an electrostatic force by a voltage applied between the through hole and the vibrating membrane adjacent to the through hole;
Including
The electrode is disposed opposite the vibrating membrane;
At least a part of the electrode portion has a larger distance from the end portion of the vibrating portion of the vibrating membrane toward the center portion in the distance between the surface of the vibrating portion of the vibrating membrane when not vibrating and the surface of the electrode portion. A display device characterized by the following shape.

Images